Vibration-based damage detection in anisotropic laminated composite beams by a shear-deformable finite element and harmony search optimization

A numerical procedure to detect and quantify damages in laminated composite beams with arbitrary lay-up using limited vibration data and harmony search optimization is presented. Since any damage in a structure changes its vibration characteristics, they can be considered as the diagnostic parameters with the help of an optimization technique. For the present study, frequencies and mode shapes are used as the damage diagnostic parameters, and the harmony search algorithm is used as the optimization tool. For finite element analyses, a five-node, thirteen-degree-of-freedom shear-deformable beam element is employed. This element can take into account the elastic couplings among extension, bending, and torsion arising due to material anisotropy existing in generally laminated composites as well as the Poisson's effect. The damage to the beam is introduced by a stiffness loss coefficient at the elemental level while mass is assumed to be unchanged. Two different objective functions to be minimized are considered for damage detection. The efficacy of the proposed method with and without the presence of noise is demonstrated by two numerically simulated composite beams including single and multiple damages. Although its accuracy somewhat decreases in case of multiple minor damages, the proposed method is successful to detect moderate and severe single and multiple damages in practice. To overcome this weakness, (i) the algorithm can be hybridized with other metaheuristics, (ii) objective function can be enhanced by combining it with other vibration characteristics such as curvature, flexibility, and so on, or (iii) two- or multi-stage damage identification methods can be considered.